Unroofing of myocardial bridge

Unroofing of myocardial bridge

Myocardial bridge is a segment of coronary artery which has an intramyocardial course. It is mostly considered as an incidental finding and is often asymptomatic. Angiographic incidence of myocardial bridge may vary from 0.5% to 16% in different series. Myocardial bridges may be associated with angina, myocardial infarction and rarely sudden cardiac death [1]. Though most myocardial bridges are left alone, some have been stented and yet others bypassed. But stent fractures have been reported  in myocardial bridges [2].

Unroofing of the myocardial bridge by surgical myotomy is another option. In one report, five symptomatic children with hypertrophic cardiomyopathy and myocardial bridge underwent supraarterial myotomy. Symptoms or evidence of myocardial ischemia resolved after the surgery [3].

A retrospective analysis of 823 adults with hypertrophic obstructive cardiomyopathy who underwent septal myectomy between 2011 and 2017 was published in 2021. 24 patients died and 7 had nonfatal myocardial infarction. The three year cumulative event free survival for all cause mortality and cardiovascular mortality was similar for those without myocardial bridges, those who had coronary artery bypass grafting, those who underwent unroofing and those who were untreated. Among the 49 patients who underwent computed tomography 1 year after surgery, the patency rate of the saphenous vein graft was significantly higher than that of left internal mammary artery (13.3% vs. 84.2%, p < .001). No myocardial bridge was detected in the unroofing group. Authors concluded that surgical treatment of myocardial bridge could be beneficial and safely performed during septal myectomy. They suggested that myocardial unroofing is the recommended treatment for myocardial bridge and unroofing when technically feasible may be preferable for long term outcome [4].

Preoperative intravascular ultrasound (IVUS) and coronary computed tomography angiography (CCTA) were evaluated in 111 patients with symptomatic myocardial bridge who underwent surgical unroofing. It was found that diastolic vessel restriction, noted in 87% of the patients on IVUS correlates with preoperative limitation of physical activity and subsequent benefit of surgical unroofing. In CCTA diastolic restriction was measured as the maximum lumen area stenosis within the myocardial bridge. Authors concluded that CCTA may be used as a noninvasive alternative to IVUS in assessing diastolic vessel restriction [5].

Another study evaluated 50 patients with myocardial bridges prospectively. They had undergone stress echocardiography, CCTA, and stress coronary angiogram with dobutamine challenge for measurement of diastolic fractional flow reserve and IVUS. Anginal symptoms were assessed by Seattle Angina Questionnaire. Patients then underwent surgical unroofing of the left anterior descending coronary artery. Follow up evaluation was done with Seattle Angina Questionnaire. They noted dramatic improvements in physical limitation due to angina, anginal stability and frequency, treatment satisfaction and quality of life. There were no major complications or deaths. Authors concluded that surgical unroofing is the optimal treatment for isolated, symptomatic, and hemodynamically significant myocardial bridges resistant to maximally tolerated medical therapy [6].

Different approaches for myocardial bridge unroofing in an analysis of 141 adults were sternotomy on-pump, sternotomy off-pump and mini thoracotomy off-pump. The numbers in each group were 40, 62 and 39 respectively [7]. Robotic totally endoscopic off-pump unroofing of left anterior descending coronary artery myocardial bridge has also been reported [8].

References

1. Mok S, Majdalany D, Pettersson GB. Extensive unroofing of myocardial bridge: A case report and literature review. SAGE Open Med Case Rep. 2019 Jan 16;7:2050313X18823380. doi: 10.1177/2050313X18823380. PMID: 30719302; PMCID: PMC6349980.
2. Tandar A, Whisenant BK, Michaels AD. Stent fracture following stenting of a myocardial bridge: report of two cases. Catheter Cardiovasc Interv. 2008 Feb 1;71(2):191-6. doi: 10.1002/ccd.21365. PMID: 18327836.
3. Downar J, Williams WG, McDonald C, Wigle ED, McCrindle BW. Outcomes after “unroofing” of a myocardial bridge of the left anterior descending coronary artery in children with hypertrophic cardiomyopathy. Pediatr Cardiol. 2004 Jul-Aug;25(4):390-3. doi: 10.1007/s00246-003-0576-2. PMID: 14749910.
4. Wang S, Wang S, Lai Y, Song Y, Cui H, Song C, Meng L, Zhu C, Wu R, Huang X. Midterm results of different treatment methods for myocardial bridging in patients after septal myectomy. J Card Surg. 2021 Feb;36(2):501-508. doi: 10.1111/jocs.15226. Epub 2020 Dec 1. PMID: 33258508.
5. Hashikata T, Honda Y, Wang H, Pargaonkar VS, Nishi T, Hollak MB, Rogers IS, Nieman K, Yock PG, Fitzgerald PJ, Schnittger I, Boyd JH, Tremmel JA. Impact of Diastolic Vessel Restriction on Quality of Life in Symptomatic Myocardial Bridging Patients Treated With Surgical Unroofing: Preoperative Assessments With Intravascular Ultrasound and Coronary Computed Tomography Angiography. Circ Cardiovasc Interv. 2021 Oct;14(10):e011062. doi: 10.1161/CIRCINTERVENTIONS.121.011062. Epub 2021 Oct 19. PMID: 34665656.
6. Boyd JH, Pargaonkar VS, Scoville DH, Rogers IS, Kimura T, Tanaka S, Yamada R, Fischbein MP, Tremmel JA, Mitchell RS, Schnittger I. Surgical Unroofing of Hemodynamically Significant Left Anterior Descending Myocardial Bridges. Ann Thorac Surg. 2017 May;103(5):1443-1450. doi: 10.1016/j.athoracsur.2016.08.035. Epub 2016 Oct 13. PMID: 27745841.
7. Wang H, Pargaonkar VS, Hironaka CE, Bajaj SS, Abbot CJ, O’Donnell CT, Miller SL, Honda Y, Rogers IS, Tremmel JA, Fischbein MP, Mitchell RS, Schnittger I, Boyd JH. Off-Pump Minithoracotomy Versus Sternotomy for Left Anterior Descending Myocardial Bridge Unroofing. Ann Thorac Surg. 2021 Nov;112(5):1474-1482. doi: 10.1016/j.athoracsur.2020.11.023. Epub 2020 Dec 14. PMID: 33333083.
8. Mirzai S, Patel B, Balkhy HH. Robotic totally endoscopic off-pump unroofing of left anterior descending coronary artery myocardial bridge: A report of two cases. J Card Surg. 2019 Aug;34(8):735-737. doi: 10.1111/jocs.14094. Epub 2019 Jun 18. PMID: 31212378.